In this final continuation year, the following experiments will be concluded: Experiment I. Was changed to determine the nature of the pigment ceroid that can be produced by crushing the epididymal fat pad in rats that had been fed for 3-4 months on diets containing a variety of fats at a level of 32%. The preliminary feeding period for this group is nearly completed now and the crushing will take place within a few weeks. Experiment II. The trials with the various forms of interceroid have run into technical difficulties in the production of interceroid in vitro. Attempts will continue to overcome these so that large amounts sufficient for feeding can be produced. Experiment III. The experiment in which rats were fed cirrhogenic diets of varying composition each modified to produce either large or trace amounts of hepatic ceroid is completed. The tissues and serum are being studied biochemically. Histologically the sections demonstrated that the feeding techniques were successful in producing livers in one group with an astonishing large amount of ceroid for contrast with livers containing little or no ceroid, but both groups having cirrhosis. The other controls turned out as planned. Experiment IV. This experiment will be started and completed in this final continuation year. The object is to determine if ceroid can act to stimulate the formation of more ceroid under appropriate conditions.